202 ME. H. B. BEADY ON PALiEOZOIC COEALS. 



they remained unaltered on a second maceration in strong acid. 

 Chemical analysis of a fair sample of the limestone showed that 

 it contained nearly thirty per cent, of silica, and that there were 

 also present sensible quantities of organic matter (bituminous), 

 free sulphur, phosphoric and sulphuric acids, and protoxide of 

 iron. 



Much fresh interest has been recently excited in the processes 

 by which the infiltration or impregnation of organic bodies with 

 silex takes place, in connection with the history of Eozoon Cana- 

 dense. In the case of Eozoon, the sarcode or animal jelly appears 

 to have been gradually replaced by siliceous material which has 

 accurately filled even the minutest tubuli of the canal-system, 

 whilst the calcareous skeleton has remained unaffected. But in 

 the corals an opposite condition is found — the skeleton has become 

 silicified, and we have no traces of the soft parts. "Whether a 

 oertain proportion of silex was secreted with the carbonate of 

 lime during the life of the animal, or whether its presence is 

 entirely due to infiltration subsequently, is a question very diffi- 

 cult of solution. 



It is well worth while, for those who have the opportunity, to 

 keep an eye on the insoluble matters turned out of the carbonic 

 acid generators in our chemical works. Carbonate of lime, in 

 many of its forms, abounds in siliceous fossils, and these are left 

 amongst the refuse thrown out ; indeed, the process of chemical 

 manufacture, as practised on the Tyne, supplies us, on a grand 

 scale, with a means of separating organic remains, which paleon- 

 tologists are prevented from employing, except in a very limited 

 way, on the ground of expense and the want of suitable appa- 

 ratus for its proper application. 



